Heretofore, there has been proposed technology that obtains a one-time password from randomly generated character strings, etc. by extracting and arranging some of the character strings or characters according to a rule determined by a user in advance. Patent Literature 1 given below discloses technology in accordance with such a one-time password, and is in accordance with the invention proposed by the present Inventor.    Patent Literature 1: U.S. Pat. No. 6,141,751